linux-kernel - Re: [PATCH v13 00/12] support "task

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Date:	Mon, 25 Jul 2016 11:35:30 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Chris Metcalf <cmetcalf@...lanox.com>
cc:	Gilad Ben Yossef <giladb@...lanox.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Andy Lutomirski <luto@...capital.net>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	linux-doc@...r.kernel.org, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v13 00/12] support "task_isolation" mode

On Fri, 22 Jul 2016, Chris Metcalf wrote:

> > It already as a stable clocksource. Sorry but that was one of the criteria
> > for the server when we ordered them. Could this be clock adjustments?
>
> We probably need to get clock folks to jump in on this thread!

Guess so. I will have a look at this when I get some time again.

> Maybe it's disabling some built-in unstable clock just as part of
> falling back to using the better, stable clock that you also have?
> So maybe there's a way of just disabling that clocksource from the
> get-go instead of having it be marked unstable later.

This is a standard Dell server. No clocksources are marked as unstable as
far as I can tell.

> If you run the test again after this storm of unstable marking, does
> it all happen again?  Or is it a persistent state in the kernel?

This happens anytime we try to run with prctl().

I hope to get some more detail once I get some time to look at this. But
this is likely an x86 specific problem.